1. Field of the Invention
This invention relates to water-based lubricants, metalworking fluids and hydraulic fluids.
2. Description of the Prior Art
Water-based metalworking fluids are known in the prior art from ASLE Transactions 7, 398-405 (1964) by Beiswanger et al. Ethoxylated phosphate esters based upon dinonylphenol or oleyl alcohol are disclosed as suited for use as additives in metalworking lubricants. The combination of a phosphate ester and a sulfur compound as additives for metalworking fluid compositions is known from U.S. Pat. No. 3,933,658. Both these prior art metalworking fluids contain phosphate esters in a mineral oil-based vehicle. The patent also discloses the use of a glycol, a mineral oil-water mixture, and a glycol-water mixture as the base vehicle.
Water-in-oil, emulsion-type hydraulic fluids are known from U.S. Pat. No. 3,222,284. Such compositions contain, in addition to mineral oil, petroleum sulfonates, and certain metal alkyl dithiophosphates. The aqueous phase is about 33 to 45 percent by weight water. A lubricating composition is disclosed in U.S. Pat. No. 3,249,538 in which about 0.5 percent by volume mineral oil is utilized in combination with a major proportion of water and molybdenum disulfide. The composition can be thickened with water-soluble polymers such as polyalkylene glycols. There is no teaching that such compositions are useful as hydraulic fluids or metalworking fluids.
In U.S. Pat. No. 4,138,346 and U.S. Pat. No. 4,151,099, water-based hydraulic fluids are disclosed comprising a phosphate ester and a sulfur containing compound or a polyester of an oxyalkylene compound and a sulfur containing compound alone or including a phosphate ester. The compositions are also useful as metalworking fluids. Both polyethylene glycol and phosphate esters are disclosed as antiwear lubricant additives.